Face seals are used in gas turbine engines to prevent the leakage of fluid along rotating shafts where the shaft extends through a stationary structure such as a wall or partition. Referring to FIG. 1, a typical face seal is comprised of a stationary stator 22, having a flat surface that rubs against a flat surface of a rotating rotor 20. The rubbing of these surfaces generates significant amounts of heat and as a result high temperatures and thermal gradients within the rotor 20 form. These thermal gradients must be managed to prevent failure of the seal. A major contributor to this adverse thermal reaction of many seals is the thermal conductive resistance within the rotor 20 which is directly related to the thermal conductivity of the material from which the rotor 20 is made. When the thermal load of the seal is not managed, the formation of coke (burned oil) at the sealing flat surface 23 can occur. Also, the adverse thermal gradients cause the flat surface 23 of the rotor 20 to swing away from the flat surface of the stator 22 resulting in leakage.
One approach to this problem has been to provide external or internal cooling of the rotor 20 in the form of oil jets or coolant passages. However, these approaches add significant complexity to the design of the rotor, are expensive, and are not always practical due to space limitations. Another approach has been to make the rotor from ceramics. A disadvantage of ceramics is their brittleness. Yet another approach is to use high conductivity copper alloys such as Copper-beryllium. However, such alloys can be too soft for many applications resulting in deformation of the rotor 20 over a period of time (a phenomenon known as "creep" deformation). This creep deformation causes the seal to become significantly out-of-flat at the sealing flat surface.
Accordingly, there is a need for a face seal having the rotor configured to dissipate heat in the most efficient manner when subjected to high thermal loads without causing creep deformation of the seal.